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Paul O’Shannessy
632 lines
36 KiB
HTML
632 lines
36 KiB
HTML
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<a href="/react/tips/introduction.html">Introduction</a>
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<a href="/react/tips/props-in-getInitialState-as-anti-pattern.html">Props in getInitialState Is an Anti-Pattern</a>
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<a href="/react/tips/dom-event-listeners.html">DOM Event Listeners in a Component</a>
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<a href="/react/tips/initial-ajax.html">Load Initial Data via AJAX</a>
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<a href="/react/tips/false-in-jsx.html">False in JSX</a>
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<a href="/react/tips/communicate-between-components.html">Communicate Between Components</a>
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<a href="/react/tips/expose-component-functions.html">Expose Component Functions</a>
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<a href="/react/tips/children-undefined.html">this.props.children undefined</a>
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<a href="/react/tips/use-react-with-other-libraries.html">Use React with Other Libraries</a>
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<li>
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<a href="/react/tips/dangerously-set-inner-html.html">Dangerously Set innerHTML</a>
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</ul>
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</div>
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</div>
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<div class="inner-content">
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<h1>
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JSXの深層
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<a class="edit-page-link" href="https://github.com/facebook/react/tree/master/docs/docs/02.1-jsx-in-depth.ja-JP.md" target="_blank">Edit on GitHub</a>
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</h1>
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<div class="subHeader"></div>
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<p><a href="https://facebook.github.io/jsx/">JSX</a>はXMLに似たJavaScriptのシンタックスの拡張です。Reactでは、単純なJSXのシンタックスの変換を使うことができます。</p>
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<h2><a class="anchor" name="jsx"></a>なぜJSXを使うのでしょうか？ <a class="hash-link" href="#jsx">#</a></h2>
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<p>ReactでJSXの使用を強制されるわけではありません。生のJSを使うこともできます。しかし、JSXは簡潔で、木構造とReactの特性を定義しやすいシンタックスであるため、JSXを使うことをお勧めします。</p>
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<p>デザイナーのようなカジュアルな開発者にとってはさらに馴染みやすいでしょう。</p>
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<p>XMLにはバランスの取れた開始タグと終了タグという利益があります。このことで、関数がオブジェクトリテラルを呼んでいるのを読むよりも簡単に大きな木構造を作ることができます。</p>
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<p>これはJavaScriptのセマンティックスを代替するものではありません。</p>
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<h2><a class="anchor" name="htmlreact"></a>HTMLタグ対Reactコンポーネント <a class="hash-link" href="#htmlreact">#</a></h2>
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<p>ReactはHTMLタグ（文字列）とReactコンポーネント（クラス）の両方をレンダリングすることができます。</p>
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<p>以下のようにJSXで小文字のタグ名を使用するだけで、HTMLタグをレンダリングできます。</p>
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<div class="highlight"><pre><code class="language-javascript" data-lang="javascript"><span class="kd">var</span> <span class="nx">myDivElement</span> <span class="o">=</span> <span class="o"><</span><span class="nx">div</span> <span class="nx">className</span><span class="o">=</span><span class="s2">"foo"</span> <span class="o">/></span><span class="p">;</span>
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<span class="nx">ReactDOM</span><span class="p">.</span><span class="nx">render</span><span class="p">(</span><span class="nx">myDivElement</span><span class="p">,</span> <span class="nb">document</span><span class="p">.</span><span class="nx">getElementById</span><span class="p">(</span><span class="s1">'example'</span><span class="p">));</span>
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</code></pre></div>
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<p>以下のように大文字から始まるローカル変数を作成するだけで、Reactのコンポーネントをレンダリングできます。</p>
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<div class="highlight"><pre><code class="language-javascript" data-lang="javascript"><span class="kd">var</span> <span class="nx">MyComponent</span> <span class="o">=</span> <span class="nx">React</span><span class="p">.</span><span class="nx">createClass</span><span class="p">({</span><span class="cm">/*...*/</span><span class="p">});</span>
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<span class="kd">var</span> <span class="nx">myElement</span> <span class="o">=</span> <span class="o"><</span><span class="nx">MyComponent</span> <span class="nx">someProperty</span><span class="o">=</span><span class="p">{</span><span class="kc">true</span><span class="p">}</span> <span class="o">/></span><span class="p">;</span>
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<span class="nx">ReactDOM</span><span class="p">.</span><span class="nx">render</span><span class="p">(</span><span class="nx">myElement</span><span class="p">,</span> <span class="nb">document</span><span class="p">.</span><span class="nx">getElementById</span><span class="p">(</span><span class="s1">'example'</span><span class="p">));</span>
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</code></pre></div>
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<p>ReactのJSXは大文字と小文字を使うことで、ローカルのコンポーネントクラスとHTMLタグを識別する習慣があります。</p>
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<blockquote>
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<p>注意:</p>
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<p>JSXはJavaScriptなので、 <code>class</code> や <code>for</code> といった識別子はXMLの属性名としては使用しません。代わりに、 ReactのDOMコンポーネントはDOMのプロパティ名がそれぞれ <code>className</code> や <code>htmlFor</code> といったものであることを期待します。</p>
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</blockquote>
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<h2><a class="anchor" name="the-transform"></a>The Transform <a class="hash-link" href="#the-transform">#</a></h2>
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<p>ReactのJSXはXMLに似たシンタックスをネイティブなJavaScriptに変換します。XML要素や属性や子要素は <code>React.createElement</code> で渡される引数に変換されます。</p>
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<div class="highlight"><pre><code class="language-javascript" data-lang="javascript"><span class="kd">var</span> <span class="nx">Nav</span><span class="p">;</span>
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<span class="c1">// 入力 (JSX):</span>
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<span class="kd">var</span> <span class="nx">app</span> <span class="o">=</span> <span class="o"><</span><span class="nx">Nav</span> <span class="nx">color</span><span class="o">=</span><span class="s2">"blue"</span> <span class="o">/></span><span class="p">;</span>
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<span class="c1">// 出力 (JS):</span>
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<span class="kd">var</span> <span class="nx">app</span> <span class="o">=</span> <span class="nx">React</span><span class="p">.</span><span class="nx">createElement</span><span class="p">(</span><span class="nx">Nav</span><span class="p">,</span> <span class="p">{</span><span class="nx">color</span><span class="o">:</span><span class="s2">"blue"</span><span class="p">});</span>
|
|
</code></pre></div>
|
|
<p><code><Nav /></code> を使うためには、 <code>Nav</code> 変数がスコープの中にないといけないことに注意してください。</p>
|
|
|
|
<p>以下のように、JSXはXMLシンタックスを使うことで、細かな子要素の使用も許可します。</p>
|
|
<div class="highlight"><pre><code class="language-javascript" data-lang="javascript"><span class="kd">var</span> <span class="nx">Nav</span><span class="p">,</span> <span class="nx">Profile</span><span class="p">;</span>
|
|
<span class="c1">// 入力 (JSX):</span>
|
|
<span class="kd">var</span> <span class="nx">app</span> <span class="o">=</span> <span class="o"><</span><span class="nx">Nav</span> <span class="nx">color</span><span class="o">=</span><span class="s2">"blue"</span><span class="o">><</span><span class="nx">Profile</span><span class="o">></span><span class="nx">click</span><span class="o"><</span><span class="err">/Profile></Nav>;</span>
|
|
<span class="c1">// 出力 (JS):</span>
|
|
<span class="kd">var</span> <span class="nx">app</span> <span class="o">=</span> <span class="nx">React</span><span class="p">.</span><span class="nx">createElement</span><span class="p">(</span>
|
|
<span class="nx">Nav</span><span class="p">,</span>
|
|
<span class="p">{</span><span class="nx">color</span><span class="o">:</span><span class="s2">"blue"</span><span class="p">},</span>
|
|
<span class="nx">React</span><span class="p">.</span><span class="nx">createElement</span><span class="p">(</span><span class="nx">Profile</span><span class="p">,</span> <span class="kc">null</span><span class="p">,</span> <span class="s2">"click"</span><span class="p">)</span>
|
|
<span class="p">);</span>
|
|
</code></pre></div>
|
|
<p>以下のように、displayNameがundefinedの時には、JSXはクラスの<a href="/react/docs/component-specs.html#displayname">displayName</a>を変数の割り当てから予測します。</p>
|
|
<div class="highlight"><pre><code class="language-javascript" data-lang="javascript"><span class="c1">// 入力 (JSX):</span>
|
|
<span class="kd">var</span> <span class="nx">Nav</span> <span class="o">=</span> <span class="nx">React</span><span class="p">.</span><span class="nx">createClass</span><span class="p">({</span> <span class="p">});</span>
|
|
<span class="c1">// 出力 (JS):</span>
|
|
<span class="kd">var</span> <span class="nx">Nav</span> <span class="o">=</span> <span class="nx">React</span><span class="p">.</span><span class="nx">createClass</span><span class="p">({</span><span class="nx">displayName</span><span class="o">:</span> <span class="s2">"Nav"</span><span class="p">,</span> <span class="p">});</span>
|
|
</code></pre></div>
|
|
<p>JSXを試し、どのようにネイティブなJavaScriptに変換されるか見るには、<a href="/react/jsx-compiler.html">JSX Compiler</a>を、すでに存在するHTMLをJSXに変換するには<a href="/react/html-jsx.html">HTMLからJSXへのコンバーター</a>を使ってください。</p>
|
|
|
|
<p>JSXを使いたい場合は、<a href="/react/docs/getting-started-ja-JP.html">始めてみましょう</a>というガイドがどのようにコンパイルを設定するか示してくれます。</p>
|
|
|
|
<blockquote>
|
|
<p>注意:</p>
|
|
|
|
<p>JSXという表現は常にReactElementを評価します。実際に実行する際の詳細はおそらく異なっているでしょう。最適化されたモードでは <code>React.createElement</code> のコードのバリデーションを避けるためにReactElementをオブジェクトリテラルとして配置するでしょう。</p>
|
|
</blockquote>
|
|
<h2><a class="anchor" name=""></a>ネームスペース化されたコンポーネント <a class="hash-link" href="#">#</a></h2>
|
|
<p>formのように、たくさんの子要素を持つコンポーネントを構築する際には、以下のように多くの変数を宣言しなければいけないでしょう。</p>
|
|
<div class="highlight"><pre><code class="language-javascript" data-lang="javascript"><span class="c1">// 変数宣言のあまりよくない部分</span>
|
|
<span class="kd">var</span> <span class="nx">Form</span> <span class="o">=</span> <span class="nx">MyFormComponent</span><span class="p">;</span>
|
|
<span class="kd">var</span> <span class="nx">FormRow</span> <span class="o">=</span> <span class="nx">Form</span><span class="p">.</span><span class="nx">Row</span><span class="p">;</span>
|
|
<span class="kd">var</span> <span class="nx">FormLabel</span> <span class="o">=</span> <span class="nx">Form</span><span class="p">.</span><span class="nx">Label</span><span class="p">;</span>
|
|
<span class="kd">var</span> <span class="nx">FormInput</span> <span class="o">=</span> <span class="nx">Form</span><span class="p">.</span><span class="nx">Input</span><span class="p">;</span>
|
|
|
|
<span class="kd">var</span> <span class="nx">App</span> <span class="o">=</span> <span class="p">(</span>
|
|
<span class="o"><</span><span class="nx">Form</span><span class="o">></span>
|
|
<span class="o"><</span><span class="nx">FormRow</span><span class="o">></span>
|
|
<span class="o"><</span><span class="nx">FormLabel</span> <span class="o">/></span>
|
|
<span class="o"><</span><span class="nx">FormInput</span> <span class="o">/></span>
|
|
<span class="o"><</span><span class="err">/FormRow></span>
|
|
<span class="o"><</span><span class="err">/Form></span>
|
|
<span class="p">);</span>
|
|
</code></pre></div>
|
|
<p>これを単純で簡単にするために、 <em>ネームスペース化されたコンポーネント</em> では、以下のように他のコンポーネントを付属物として持つ1つのコンポーネントを使うことができます。</p>
|
|
<div class="highlight"><pre><code class="language-javascript" data-lang="javascript"><span class="kd">var</span> <span class="nx">Form</span> <span class="o">=</span> <span class="nx">MyFormComponent</span><span class="p">;</span>
|
|
|
|
<span class="kd">var</span> <span class="nx">App</span> <span class="o">=</span> <span class="p">(</span>
|
|
<span class="o"><</span><span class="nx">Form</span><span class="o">></span>
|
|
<span class="o"><</span><span class="nx">Form</span><span class="p">.</span><span class="nx">Row</span><span class="o">></span>
|
|
<span class="o"><</span><span class="nx">Form</span><span class="p">.</span><span class="nx">Label</span> <span class="o">/></span>
|
|
<span class="o"><</span><span class="nx">Form</span><span class="p">.</span><span class="nx">Input</span> <span class="o">/></span>
|
|
<span class="o"><</span><span class="err">/Form.Row></span>
|
|
<span class="o"><</span><span class="err">/Form></span>
|
|
<span class="p">);</span>
|
|
</code></pre></div>
|
|
<p>これを行うためには、以下のようにメインコンポーネントの付属物として、「サブコンポーネント」を作るだけで大丈夫です。</p>
|
|
<div class="highlight"><pre><code class="language-javascript" data-lang="javascript"><span class="kd">var</span> <span class="nx">MyFormComponent</span> <span class="o">=</span> <span class="nx">React</span><span class="p">.</span><span class="nx">createClass</span><span class="p">({</span> <span class="p">...</span> <span class="p">});</span>
|
|
|
|
<span class="nx">MyFormComponent</span><span class="p">.</span><span class="nx">Row</span> <span class="o">=</span> <span class="nx">React</span><span class="p">.</span><span class="nx">createClass</span><span class="p">({</span> <span class="p">...</span> <span class="p">});</span>
|
|
<span class="nx">MyFormComponent</span><span class="p">.</span><span class="nx">Label</span> <span class="o">=</span> <span class="nx">React</span><span class="p">.</span><span class="nx">createClass</span><span class="p">({</span> <span class="p">...</span> <span class="p">});</span>
|
|
<span class="nx">MyFormComponent</span><span class="p">.</span><span class="nx">Input</span> <span class="o">=</span> <span class="nx">React</span><span class="p">.</span><span class="nx">createClass</span><span class="p">({</span> <span class="p">...</span> <span class="p">});</span>
|
|
</code></pre></div>
|
|
<p>JSXはコードをコンパイルする際にこのプロパティをハンドルします。</p>
|
|
<div class="highlight"><pre><code class="language-javascript" data-lang="javascript"><span class="kd">var</span> <span class="nx">App</span> <span class="o">=</span> <span class="p">(</span>
|
|
<span class="nx">React</span><span class="p">.</span><span class="nx">createElement</span><span class="p">(</span><span class="nx">Form</span><span class="p">,</span> <span class="kc">null</span><span class="p">,</span>
|
|
<span class="nx">React</span><span class="p">.</span><span class="nx">createElement</span><span class="p">(</span><span class="nx">Form</span><span class="p">.</span><span class="nx">Row</span><span class="p">,</span> <span class="kc">null</span><span class="p">,</span>
|
|
<span class="nx">React</span><span class="p">.</span><span class="nx">createElement</span><span class="p">(</span><span class="nx">Form</span><span class="p">.</span><span class="nx">Label</span><span class="p">,</span> <span class="kc">null</span><span class="p">),</span>
|
|
<span class="nx">React</span><span class="p">.</span><span class="nx">createElement</span><span class="p">(</span><span class="nx">Form</span><span class="p">.</span><span class="nx">Input</span><span class="p">,</span> <span class="kc">null</span><span class="p">)</span>
|
|
<span class="p">)</span>
|
|
<span class="p">)</span>
|
|
<span class="p">);</span>
|
|
</code></pre></div>
|
|
<blockquote>
|
|
<p>注意:
|
|
この特徴は <a href="/react/blog/2014/07/17/react-v0.11.html#jsx">v0.11</a> 以上で使用できます。</p>
|
|
</blockquote>
|
|
<h2><a class="anchor" name="javascript"></a>JavaScriptの表現 <a class="hash-link" href="#javascript">#</a></h2><h3><a class="anchor" name=""></a>アトリビュートの表現 <a class="hash-link" href="#">#</a></h3>
|
|
<p>JavaScriptで書いたものをアトリビュートの値として使うためには、その表現を引用(<code>""</code>)ではなく波括弧(<code>{}</code>)で囲ってください。</p>
|
|
<div class="highlight"><pre><code class="language-javascript" data-lang="javascript"><span class="c1">// 入力 (JSX):</span>
|
|
<span class="kd">var</span> <span class="nx">person</span> <span class="o">=</span> <span class="o"><</span><span class="nx">Person</span> <span class="nx">name</span><span class="o">=</span><span class="p">{</span><span class="nb">window</span><span class="p">.</span><span class="nx">isLoggedIn</span> <span class="o">?</span> <span class="nb">window</span><span class="p">.</span><span class="nx">name</span> <span class="o">:</span> <span class="s1">''</span><span class="p">}</span> <span class="o">/></span><span class="p">;</span>
|
|
<span class="c1">// 出力 (JS):</span>
|
|
<span class="kd">var</span> <span class="nx">person</span> <span class="o">=</span> <span class="nx">React</span><span class="p">.</span><span class="nx">createElement</span><span class="p">(</span>
|
|
<span class="nx">Person</span><span class="p">,</span>
|
|
<span class="p">{</span><span class="nx">name</span><span class="o">:</span> <span class="nb">window</span><span class="p">.</span><span class="nx">isLoggedIn</span> <span class="o">?</span> <span class="nb">window</span><span class="p">.</span><span class="nx">name</span> <span class="o">:</span> <span class="s1">''</span><span class="p">}</span>
|
|
<span class="p">);</span>
|
|
</code></pre></div><h3><a class="anchor" name="boolean"></a>Booleanのアトリビュート <a class="hash-link" href="#boolean">#</a></h3>
|
|
<p>アトリビュートの値を記述しないと、JSXはそれを <code>true</code> として扱ってしまいます。<code>false</code> を渡すためには、アトリビュートが使われる必要があります。これらはHTMLのform要素の <code>disabled</code> 、 <code>required</code> 、 <code>checked</code> 、 <code>readOnly</code> といったアトリビュートを使う際によく見かけられます。</p>
|
|
<div class="highlight"><pre><code class="language-javascript" data-lang="javascript"><span class="c1">// 以下の2つはボタンを使用不能にするという意味でJSXでは同義です。</span>
|
|
<span class="o"><</span><span class="nx">input</span> <span class="nx">type</span><span class="o">=</span><span class="s2">"button"</span> <span class="nx">disabled</span> <span class="o">/></span><span class="p">;</span>
|
|
<span class="o"><</span><span class="nx">input</span> <span class="nx">type</span><span class="o">=</span><span class="s2">"button"</span> <span class="nx">disabled</span><span class="o">=</span><span class="p">{</span><span class="kc">true</span><span class="p">}</span> <span class="o">/></span><span class="p">;</span>
|
|
|
|
<span class="c1">// 以下の2つはボタンを使用不能にしないという意味でJSXでは同義です。</span>
|
|
<span class="o"><</span><span class="nx">input</span> <span class="nx">type</span><span class="o">=</span><span class="s2">"button"</span> <span class="o">/></span><span class="p">;</span>
|
|
<span class="o"><</span><span class="nx">input</span> <span class="nx">type</span><span class="o">=</span><span class="s2">"button"</span> <span class="nx">disabled</span><span class="o">=</span><span class="p">{</span><span class="kc">false</span><span class="p">}</span> <span class="o">/></span><span class="p">;</span>
|
|
</code></pre></div><h3><a class="anchor" name=""></a>子要素の表現 <a class="hash-link" href="#">#</a></h3>
|
|
<p>同様に、JavaScriptは子要素を表現するのに使われることもあります。</p>
|
|
<div class="highlight"><pre><code class="language-javascript" data-lang="javascript"><span class="c1">// 入力 (JSX):</span>
|
|
<span class="kd">var</span> <span class="nx">content</span> <span class="o">=</span> <span class="o"><</span><span class="nx">Container</span><span class="o">></span><span class="p">{</span><span class="nb">window</span><span class="p">.</span><span class="nx">isLoggedIn</span> <span class="o">?</span> <span class="o"><</span><span class="nx">Nav</span> <span class="o">/></span> <span class="o">:</span> <span class="o"><</span><span class="nx">Login</span> <span class="o">/></span><span class="p">}</span><span class="o"><</span><span class="err">/Container>;</span>
|
|
<span class="c1">// 出力 (JS):</span>
|
|
<span class="kd">var</span> <span class="nx">content</span> <span class="o">=</span> <span class="nx">React</span><span class="p">.</span><span class="nx">createElement</span><span class="p">(</span>
|
|
<span class="nx">Container</span><span class="p">,</span>
|
|
<span class="kc">null</span><span class="p">,</span>
|
|
<span class="nb">window</span><span class="p">.</span><span class="nx">isLoggedIn</span> <span class="o">?</span> <span class="nx">React</span><span class="p">.</span><span class="nx">createElement</span><span class="p">(</span><span class="nx">Nav</span><span class="p">)</span> <span class="o">:</span> <span class="nx">React</span><span class="p">.</span><span class="nx">createElement</span><span class="p">(</span><span class="nx">Login</span><span class="p">)</span>
|
|
<span class="p">);</span>
|
|
</code></pre></div><h3><a class="anchor" name=""></a>コメント <a class="hash-link" href="#">#</a></h3>
|
|
<p>JSXにコメントを加えるのは簡単です。ただのJSの書き方です。タグの内側にコメントを書く時には、 <code>{}</code> で囲うことに注意してください。</p>
|
|
<div class="highlight"><pre><code class="language-javascript" data-lang="javascript"><span class="kd">var</span> <span class="nx">content</span> <span class="o">=</span> <span class="p">(</span>
|
|
<span class="o"><</span><span class="nx">Nav</span><span class="o">></span>
|
|
<span class="p">{</span><span class="cm">/* 子要素にコメントを書く時には、 {} で囲う */</span><span class="p">}</span>
|
|
<span class="o"><</span><span class="nx">Person</span>
|
|
<span class="cm">/* 複数</span>
|
|
<span class="cm"> 行</span>
|
|
<span class="cm"> コメント */</span>
|
|
<span class="nx">name</span><span class="o">=</span><span class="p">{</span><span class="nb">window</span><span class="p">.</span><span class="nx">isLoggedIn</span> <span class="o">?</span> <span class="nb">window</span><span class="p">.</span><span class="nx">name</span> <span class="o">:</span> <span class="s1">''</span><span class="p">}</span> <span class="c1">// 行末コメント</span>
|
|
<span class="o">/></span>
|
|
<span class="o"><</span><span class="err">/Nav></span>
|
|
<span class="p">);</span>
|
|
</code></pre></div>
|
|
<blockquote>
|
|
<p>注意:
|
|
JSXはHTMLに似ていますが、全く同じではありません。いくつかのキーの違いについては<a href="/react/docs/jsx-gotchas.html">JSXの理解</a> をご覧ください。</p>
|
|
</blockquote>
|
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<a class="docs-prev" href="/react/docs/displaying-data-ja-JP.html">← Prev</a>
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<a class="docs-next" href="/react/docs/jsx-spread-ja_JP.html">Next →</a>
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A Facebook & Instagram collaboration.<br>
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<a href="/react/acknowledgements.html">Acknowledgements</a>
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</div>
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© 2013–2016 Facebook Inc.<br>
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Documentation licensed under <a href="https://creativecommons.org/licenses/by/4.0/">CC BY 4.0</a>.
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